Zoomcar charges manipulation

I ordered zoomcar on 9Dec 2016. In traffic, I touched the car to an auto and inflicted damage. On returning the car, 2 damages were present on the car, 1 on the bumper and 1 on the driver side door. After booking completion, I asked zoomcar helpline number to state me the breakdown of charges, they stated 2000 Rupees for damage on bumper and 2000 Rupees for damage on door. Later, I found that the damage was there beforehand pickup of the car, it was visible in a video taken by me before pickup. I sent them the videos and after that they changed the explanation that 4000 Rupees were charged for only one damage on the bumper. Their policy states that they can charge 7000 Rupees for damage on bumper. Can I do anything about this fraudulent behaviour of changing reasons for charges? Conversations with the agents can probably prove that they changed the charge-breakdown but I don't have recording. I have a mail in which an agent writes in context of damage on the door. They have been rejecting to respond logically instead they are giving scripted diplomatic answers. What to do? I have not agreed to pay to them on such conditions, they are saying that they will take legal action upon this rejection of payment. PS: I have paid 5000 for security deposit but the total charges applied exceed by about 1200 Rupees. Help!